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Piston/Turbine Engine

The next step!
  (+3, -1)
(+3, -1)
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I propose a turbine engine however instead of a traditional compressor fan arrangement, the compressor fan is replaced by a conventional layout IC engine block and cylinders. Such Turbines would be considerably smaller than their helicopter based counterparts and would put out correspondingly less HP but at greater efficiency than a traditional ICE.

This approach would permit rapid introduction into the auto market as the layout of the engine would be nearly identical to a traditional ICE but it would also allow for conversion of existing engines with a bolt on kit very similar to a Supercharger installation but in reverse.

jhomrighaus, Aug 27 2007

Motorjet http://en.wikipedia.org/wiki/Motorjet
There's a reason you don't hear about them. [elhigh, Aug 28 2007]


       I'm sure it wouldn't be too hard (although expensive) to make a prototype, with just a small air compressor and model-size turbine. [+]
acurafan07, Aug 27 2007

       I would think a turbocharged IC engine would be more efficient.
Livingfishguy, Aug 27 2007

       Why would you think that out of curiosity?
jhomrighaus, Aug 27 2007

       I'm confused--you're using a set of pistons to compress the air, which is then routed into a conventional turbine combustion chamber and power fan? If so, it sounds like a terrible idea--the compression fan is probably the simplest part of a turbine engine, and you're replacing it with dozens of moving parts, with a corresponding increase of mechanical friction and wear. If it even works, which I don't think it would.
5th Earth, Aug 27 2007

       I'm confused, too. Are you powering a compressor fan with a piston engine, or somehow getting compressed air out of //a conventional layout IC engine block and cylinders//?? You don't mention how the air is compressed, you just say to replace a fan with an engine. Do you mean to power the fan WITH an engine?   

       If you mean--guessing from your last paragraph--to compress air for a turbine powerplant by using an piston-powered compressor/fan, it's been done.   

       I recall a page in one of Bill Gunston's books, Jet and Turbine Engines (or something like that) where he mentioned two similar-but-opposite turbine engine designs. One powered the compressor with a piston engine, the other had a huge axial-flow compressor for a piston engine. Neither worked well.   

       This is one of those areas that's been completely worked over by highly-paid researchers and barely-sane garage tinkerers. It's hard to come up with something new and workable for engines, whether turbine or piston.
baconbrain, Aug 27 2007

       To begin, let us first note the location which this idea has been posted(ie the half-bakery)   

       What I am proposing is that the piston engine be converted into an air compressor(change valve timing) and that the compressed air that is produced is fed to a combustion chamber which feeds a Turbine for power. The turbine output shaft is connected to the crank shaft of the engine and as such provides power to the compressor and the transmission.   

       I am not espousing this as anything other than a half-baked way to quickly integrate turbines into existing car designs and drive-train layouts.
jhomrighaus, Aug 27 2007

       So what powers the piston engine?
Texticle, Aug 27 2007

       The Turbine powers the piston compressor(as in a normal turbine system)
jhomrighaus, Aug 27 2007

       Okay, a high-speed turbine driving a piston compressor made from a standard engine. I can see that now in the original idea's text. But it could have been clearer.   

       That is new to me, I must admit, which may be why I didn't get it at first. Well, it would take a good reduction system, but you'd need that for the drivetrain anyhow. So it might work.   

       My first doubt relates to the amount of airflow. A standard piston engine puts out enough air to drive perhaps a three-inch turbine, based on the turbines that are found in superchargers. If the engine is converted to a "two-stroke" compressor, it may move twice as much. I'm guessing a turbine engine of comparable horsepower would need more airflow, but that's a guess.   

       i do know that some model-airplane turbine engines are started with a bicycle pump.
baconbrain, Aug 27 2007

       [Bacon] beat me to it: a conventional piston engine isn't going to generate the volume of gas you want for driving a turbine, unless the pistons are GIGANTIC.   

       There are ways to do it that (sort of) make sense. But then the exhaust path from the piston needs to be tiny to keep the gas charge from expanding into uselessness on its way to the power turbine.   

       Is the idea to do the combusting in the turbine or in the engine? If it's the engine, then I think this is baked in the form of turbocompounding, which Scania has done some work on, and if it isn't then I think what you're trying to invent is the Motorjet. (link)   

       Okay, I read one of your comments better and now I see the combustion is in the turbine. Good. That means the gigantic pistons can be very lightweight. Expand on that and make them double-acting, compressing from both the top and bottom of the piston so there is no wasted motion. A turbine wants a lot of air, so you can't really afford a dead spot.
elhigh, Aug 28 2007

       If it were the other way around, i.e beginning conceptually with a turbine engine and replacing the turbine bit with an IC engine, you would have a centifugally-supercharged IC engine like that in, say, a 1938 Graham or such.   

       I remember one of Stan Mott's Cyclops pieces where the latest turbocharged Cyclops generated more torque at the turbocharger shaft than the crankshaft, and therefore had the transmission running off the former, with the crank spinning free.   

       There is a fascinating grey area in which piston engines gradually become turbines, and vice versa. [+] for going there.
Ned_Ludd, Aug 28 2007


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